Die Heating In Production

ABSTRACT --- Extrusion dies have to be pre-heated before they are loaded into the
extrusion press. If dies are not heated to the correct temperature, there is the risk of
premature die failure, incorrect metal flow and sticking billets. Most extrusion plants set
the die oven at a fixed temperature in the range 450o  500oC and rely on time to control
the temperature. In many plants there has been a significant increase in the number of
die changes per shift, but no increase in heating capacity reducing the individual die
heating time. This paper discusses the factors that control die heating, and presents
some practical results of heating trials using a die set fitted with thermocouples. The
trials were carried out in several different ovens showing the temperature changes with
time. The results give a practical indication of the minimum time needed to adequately
preheat a die. Another problem is the effect of the die bearing being exposed to the
furnace atmosphere. Polished samples of H13 die steel were placed in a die oven for
different times and then removed. The changes in the surface are described.